The sins of the fathers should not be laid on their children. Helping people alive today who are disadvantaged is a fine goal

We have built an entire system based on the majority race and culture of the people who have stolen the land. That system is the systemic racism that is talked about. Giving a voice to that culture that has been taken from seems like a way to undo that systemic racism. To help understand where we've built racism systemically into our system.

trying to divvy those groups up on the basis of ethnicity or ancestry is simply repeating the original problem.

It is not at all. This is only true if you believe giving a voice is equal to giving over full control of the government. It's not the case at all.

ever once having to make decisions on the basis of who’s grandfathers belonged to which families and have what genetic profiles.

Technically this is a culture of tribes rather than genetic profiles. So the entire committee could have been entirely white folks who were picked by the tribes to represent their culture. Has nothing to do with race or genetics. Assuming it did is like assuming Australians are all white.